Not sure if this helps the debate but just in case:
ICAO DOC 9643 (copy infront of me) is the document that describes the applicable separations during multiple runway operations and was the basis for the recent design work for Mixed-mode and Runway Three at Heathrow; this document always refers to track when describing separation requirements. For example, during parallel runway ops. the missed approach track from one runway must diverge by 30 degrees or more from the initial departure track from a parallel runway.
Therefore, I would say where instructions are being given to ensure separation it seems probable that heading should never come into it - we should always be dealing in track (unless, of course, one issues a heading that allows for the drift).
Point 4